Wellbore packers are known that are used to create a seal in a wellbore. The term “wellbore packer” may be used to also encompass a bridge plug, a straddle tool, etc., all of which are employed in wellbore operations to control fluid flow. A wellbore packer is deployed in a well to be expanded between a mandrel and a constraining wall, such as an open wellbore wall, a lined wellbore wall or another liner. The mandrel may have an open bore or may be sealed against fluid flow. The mandrel is often part of a larger structure, such as a wellbore string.
Sometimes, a wellbore tool is needed that operates both to create a seal about, and anchor, the mandrel in a wellbore. Such a tool has a requirement for both a sealing mechanism and an anchoring mechanism. As such, some packers have both a sealing element and mechanism for expanding that sealing element and a separate anchoring slip system and a mechanism for driving the slips against the constraining wall in which the tool is positioned.
The packing element is often formed of deformable materials such as rubber or other elastomers and is squeezed with compression, either mechanically applied or hydraulically applied. When the packing element is squeezed out, it expands radially outwardly and is driven into contact against the constraining wall in which the tool is positioned. At the same time, the backside of the packing element is sealed up against the mandrel and a seal is achieved. The best seal is achieved when the packing element is kept from axially extruding, as such extrusion may lead to seal damage and failure.
The anchoring slip system, for example, may include a cone system including an inclined frustoconical wedge that forces the slip against the constraining wall in which the tool is positioned. It may also contain a ratcheting device called a mandrel lock that locks the slip in the anchored position.
The anchoring slip system is offset axially along the mandrel from the packing element.